Security devices are used to protect a computer network from unauthorized, malicious, or disruptive users. Examples of security devices include firewalls, Intrusion Detection Systems (IDSs), Intrusion Prevention Systems (IPSs), Unified Threat Management (UTM) systems, and the like.
Some security devices are flow based (e.g., also known as stateful security devices). Flow based security devices typically store information regarding flows associated with received packets. Flow based security devices can perform security processing (e.g., determining whether to drop a packet or allow the packet to pass) using the stored information regarding flows. Typically, a flow based security device stores information regarding flows in a flow table (e.g., also known as a session table or a state table).